Recovery of sulphur



Patented Aug. 9, 1932 UNITED STATES PATENT GFFIQE RAYMOND F. BACON, 0FBBONXVILLE, AND ISAAC BENCOWI'I'Z, OF NEW YORK, N. Y.; SAID BENCOWITZASSIGNOR TO SAID BACON RECOVERY or SULPHUR No Drawing.

This invention relates to the recovery of sulphur and has for an objectthe provision of an improved process for recovering sulphur from heavymetal sulphide ores. More particularly, the invention contemplates theprovision of an improved process for recovering sulphur from materialscontaining one or more sulphides of iron. The invention furthercontemplates the provision of an improved process for treating metalsulphide ores such, for example, as ore containing sulphides of iron,copper and nickel.

The process of the present invention involves the treatment of ore orother metallurgical raw materials or products containing pyrites orother sulphides of iron, alone or in combination with sulphides of otherheavy metals, such, for example, as copper and nickel with hydrogenchloride for the purpose of obtaining free sulphur.

The present invention is based on our discovery that react-ions betweenhydrogen chloride and pyrites are promoted by small amounts of watervapor and oxygen. When pyritesbearing material is heated in the presenceof hydrogen chloride and small amounts of water vapor and oxygen undersuitably controlled conditions, hydrogen sulphide, sulphur dioxide andferrous chloride are produced. Oxides of iron and other heavy metalswhich may be present in the material being treated may also be produced,but the reactions may be so controlled that substantially all of thepyrites is converted to ferrous chloride and substantially all otherheavy metal sulphides such, for example, as copper and nickel sulphides,which may be present in the sulphide-bearing ma terial may be convertedinto the corresponding chlorides. In an ordinary commercial operation,the iron remaining after treatment of pyrites-bearing material will bepresent in the form of ferric oxide and ferrous chloride. The relativeamounts of ferrous chloride and ferric oxide produced will be determinedby the temperature employed and the quantities of water vapor and oxygenpresent during the course of the reaction. At relatively lowtemperatures, substantially complete conversion of the pyrites to fer-Application filed July 30, 1930. Serial No. 471,889.

rous chloride may be accomplished in the presence of relatively largeamounts of water vapor. At relatively high temperatures, it is advisableto employ relatively small amounts of water vapor in order to effect aconversion of substantial amounts of pyrites to ferrous chloride. Theamount of water vapor employed in conjunction with the hydrogen chlorideand oxygen will be determined by the results desired. The necessaryamount of water vapor may be provided by introducing the pyrites-bearingmaterial into the reaction chamber in a damp, moist, or wet condition.In general, an amount of water suficient to utilize the heat generatedin the reaction of the oxygen with the pyrites may be employed.

The reactions involved will take place satisfactorily at temperaturesabove 300 (1, but at relatively low temperatures the reactions proceedvery slowly. Temperatures between 350 C. and 550 C. may be usedadvantageously, and at such temperatures only suiiicient water vapor toserve in the capacity of a catalyst should be employed. Ordinarily, amaximum temperature of about 500 C. is entirely satisfactory.

A complete process of the invention involves the treatment ofpyrites-bearing material with hydrogen chloride, water vapor and oxygento produce hydrogen sulphide and sulphur dioxide. The oxygen may beprovided by mixing air with the hydrogen chloride or with the hydrogenchloride and water vapor. We prefer to so conduct the operation that asubstantially complete conversion of pyrites to ferrous chloride isefiected. The hydrogen sulphide and sulphur dioxide produced are causedto react to liberate elemental sulphur. In order to produce elementalsulphur, the hydrogen sulphide and sulphur dioxide are preferably passedin contact with c a catalytic agent capable of promoting the desiredreaction. The treatment of pyritesbearing material is so conducted thatferrous chloride and chlorides of other heavy metals which may bepresent in the material being treated are produced. The resultingchloride-bearing material may be treated to regenerate hydrogen chlorideto be returned to the process.

The relative amounts of sulphur dioxide and hydrogen sulphide producedmay be controlled by regulating the amounts of hydrogen chloride, airand water vapor employed. The process may be so controlled that twomolecules of hydrogen sulphide are produced for every molecule ofsulphur dioxide produced, or, it may be so controlled'that any desiredrelative amounts of the compounds may be produced and any additionalamount of either compound which may be required for the production ofelemental sulphur may be supplied from. a separate source.

According to the preferred process of the invention, twoor more separateoperations for the production of mixtures of sulphur dioxide andhydrogen sulphide are conducted simultaneously, and the resulting gasesare combined for the purpose of the operation for producing elementalsulphur. It is difficult to so control a single operation as to producethe theoretical amounts of sulphur dioxide and hydrogen sulphiderequired for carrying out the reaction for the production of elementalsulphur, but an operation may be readily adjusted to produce mixtures ofgases containing fixed proportions of hydrogen sul- -phid'e and sulphurdioxide with either in excess. We, therefore, prefer to conduct two ormore separate operations to produce different mixtures of gasescontaining hydrogen sulphide andsulphur dioxide in difi'erentproportions but all of which may be combined to produce a mixturecontaining hydrogen sulphide and sulphur dioxide in proper pro portions.This procedure permits all of the operations to be conductedcontinuously without frequent adjustments, or, if the combined gasesshow a tendency to vary, one of the operations may be used for controlpurposes.

The invention will be better understood from a consideration of thefollowing description of a process for treating ore containing pyritesand sulphides of copper and nickel. The ore to be treated is introducedin a finely divided condition into the interiors of two similar rotaryreaction chambers, each having ore charging means at one end anddischarging means at the other end, and which are so constructed andoperated that the ore is gradually moved from the charging ends towardthe discharge ends. Hydrogen chloride, air and water vapor areintroduced into the reaction chambers at the ends opposite to those inwhich the ore is introduced, and the ore and hydrogen chloride, air andwater vapor pass through the reaction chambers in countercurrentrelationship, the hydrogen sulphide and sulphur dioxide producedbeing'removed from the reaction chambers at points near the chargingends. All or any desired portion of the water vapor required may beprovided by introducing the ore into the reaction chambers in a damp,moist or wet condition.

The ore is preferably ground to provide particles sufficiently small topass a lOO-mesh screen in order that intimate contact of the sulphideparticles with the water vapor, air and hydrogen chloride may beobtained.

The reactions involved proceed satisfacs torily at temperatures as low'as 300 C. but they proceed very rapidly and more completely at atemperature of about 550 C. It is therefore advisable to maintainatemperatune of about 550 C. in at least a portion of each reactionchamber and to so control the amounts of air and water vapor present inthe gaseous reagent mixture that substantially complete conversion ofthe pyrites to ferrous chloride is efi'ected in a suitably short periodof time. Such a temperature may be maintained in the charging endportions of the reaction chambers to insure the passage of all issuinggases through zones in which conditions are conducive to a complete andrapid reaction.

The process is preferably so controlled that a temperature of about 550C. is maintained near the charging end of the reaction chambers and atemperature of about 300 C. to 400 C. is maintained at the disglgrargeend portions of the reaction cham- The hydrogen chloride, air andwatervapor are introduced into portions of the reaction chambers whichare maintained at a temperature of 300 C. to 400 C. The hydrogenchloride and the metal sulphides in the presence of the air and watervapor react to produce sulphur dioxide, hydrogen sulphide, ferrouschloride and the chlorides of copper and nickel. The chlorides producedand the gangue materials of the original ore are discharged continuouslyin the form of a solid residue. Small amounts of hydrogen sulphide andsulphur dioxide react within the reaction chambers to produce elementalsulphur which is vaporized. The gases issuing from the reaction chambersare mixtures comprising hydrogen sulphide, sulphur dioxide, water vapor,nitrogen, elemental sulphur and small amounts of hydrogen chloride. 7

One of the reaction chambers is preferably operated under constantconditions with respect to temperature and amounts of ore and reagentsintroduced. The other reaction chamber is preferably utilized forcontrol purposes and operated under variable controlled conditions. Thevariable operation is so conducted that the gases from the two chambersmay be combined to provide hydrogen sulphide and sulphur dioxide inproper proportions for carrying out the reaction for .0

producing elemental sulphur according to the following equation:

The mixture of gases is cooled to condense the sulphur vapor containedtherein, and the remaining gases are passed in contact With water. Forbringing the gases into contact with water, the gases and water may bepassed in countercurrent relationship through a packed tower. Thehydrogen chloride contained in the gases is dissolved in the water toform a dilute solution of hydrochloric acid which promotes a reactionbetween the hydrogen sulphide and the sulphur dioxide. Elemental sulphuris formed and it may be separated from the hydrochloric acid solution inany desired manner as, for example, by settling and decantation orfiltering.

The hot residue containing the heavy metal chlorides and oxides may betreated in any desired manner to regenerate hydrogen chloride and/or toremove the metal values.

We claim:

1. In a process for treating pyrites-bearing material to recovlersulphur, the improvement which comprises subjecting the material to theaction of hydrogen chloride in the persence of water vapor and oxygen.

2. In a process for treating pyrites-bea-ring material to recoversulphur, the improvement which comprises subjecting the material at anelevated temperature to the action of hydrogen chloride in the presenceof water vapor and oxygen, and controlling the amounts of water vaporand oxygen employed to control the amount of ferrous chloride produced.

3. In a process for treating pyrites-bearing material to recoversulphur, the improvement which comprises subjecting the material to theaction of hydrogen chloride in the presence of water vapor and oxygenand controlling the amounts of water vapor and oxygen to control theamounts of hydrogen sulphide, sulphur dioxideand ferrous chlorideproduced.

4. In a process for treating pyrites-bearing material to recoversulphur, the improvement which comprises subjecting the material in adamp or wet condition and in the presence of oxygen to the action ofhydrogen chloride at an elevated temperature.

In testimony whereof We affix our signatures.

RAYIIOND F. BACON. ISAAC BENCOWITZ.

